Trodusquemine (MSI-1436): A Comprehensive Profile of a Novel Aminosterol PTP1B Inhibitor

II. Introduction to Trodusquemine (MSI-1436)

A. Overview and Significance

Trodusquemine, identified by DrugBank Accession Number DB06333 and also widely recognized by its investigational designation MSI-1436, is a naturally occurring aminosterol derived as a spermine metabolite of cholesterol.[1] This small molecule has attracted considerable scientific attention primarily due to its potent and selective inhibition of Protein Tyrosine Phosphatase 1B (PTP1B).[1] PTP1B is a pivotal negative regulator within the insulin and leptin signaling cascades, making it a significant target for metabolic diseases.[4]

The therapeutic potential of Trodusquemine is underscored by an exceptionally broad spectrum of activities demonstrated in preclinical studies. These include, but are not limited to, anti-obesity, anti-diabetic, neuroprotective, cardioprotective, tissue regenerative, and anticancer effects.[2] Such diverse pharmacological actions position Trodusquemine as a compound of substantial interest for addressing multiple complex human diseases, many of which are characterized by high unmet medical needs. Its natural origin, coupled with a unique allosteric mechanism of PTP1B inhibition, distinguishes it from many synthetically derived PTP1B inhibitors. The compound's journey from a natural isolate to a candidate for various human ailments highlights the intricate relationship between natural product chemistry and modern drug discovery.

B. Brief History of Discovery

Trodusquemine was originally isolated from liver extracts of the spiny dogfish shark, Squalus acanthias.[2] Its discovery was not initially aimed at metabolic diseases but rather stemmed from research endeavors focused on identifying novel antimicrobial compounds within Squaliformes.[2] Sharks of this order are known to possess a robust innate immune system, suggesting a reliance on endogenous antimicrobial agents rather than a highly developed adaptive immune response.[2] This initial context, focusing on its antimicrobial properties [2], preceded the later elucidation of its more widely studied PTP1B inhibitory actions and the consequent exploration of its metabolic and regenerative potential.

The dual nature of Trodusquemine's initial scientific interest—first as an antimicrobial agent and subsequently as a PTP1B inhibitor with profound metabolic and regenerative implications—suggests a molecule with pleiotropic actions, capable of interacting with multiple biological systems. The initial discovery as part of a search for antimicrobials in sharks [2], combined with its demonstrated broad-spectrum antimicrobial activity [2], and the later identification of its potent PTP1B inhibition leading to diverse therapeutic effects [1], points towards interactions with fundamental cellular processes or multiple molecular targets. This complexity, while challenging to dissect, also signifies a rich pharmacological profile ripe with therapeutic possibilities.

Furthermore, the developmental trajectory of Trodusquemine, from a natural product isolated from a marine organism to a clinical candidate investigated for human diseases such as obesity, type 2 diabetes, metastatic breast cancer, and more recently Dystrophinopathies [10], underscores the enduring importance of natural product discovery in contemporary medicine. This is true even for complex, non-infectious diseases. Natural products often possess unique chemical scaffolds and mechanisms of action that are not readily found in synthetic compound libraries. Trodusquemine's allosteric inhibition of PTP1B serves as a prime example of such novelty.[2] Despite inherent challenges in supply from natural sources and the complexities of its synthesis [3], the unique biological activities presented by such molecules often justify the extensive research and development efforts. This reinforces the value of bioprospecting unique biological niches and investigating the pharmacopeia of organisms like sharks, which have evolved distinct survival mechanisms.

III. Chemical Profile and Physicochemical Properties

A. Nomenclature and Identifiers

Trodusquemine is the generic name for this investigational small molecule.[1]

• DrugBank Accession Number: DB06333 [1]
• CAS Number (free base): 186139-09-3 [1]
• Synonyms: MSI-1436, MSI-1436C, Aminosterol 1436, Produlestan, Trodulamine.[2] The designation MSI-1436 is frequently encountered in scientific literature.
• Salt Forms:
• Trodusquemine hydrochloride: UNII 7VON0S1S42. The molecular formula is C37​H75​Cl3​N4​O5​S, with a molecular weight of 794.4 g/mol. PubChem CID for the hydrochloride is 76957349.[1]
• Trodusquemine lactate: CAS 1309370-86-2.[3]
• Trodusquemine phosphate: CAS 1309370-85-1.[15] The existence of multiple synonyms and various salt forms is a common occurrence during the drug development process.

B. Molecular Structure and Formula

For the free base form of Trodusquemine:

• Molecular Formula: C37​H72​N4​O5​S [3]
• Molecular Weight: 685.066 g/mol [3]
• Exact Mass: 684.522 Da [3] (also reported as 684.52 Da [15])

Trodusquemine is classified as an aminosterol, specifically a spermine metabolite of cholesterol. Its complex structure consists of a cholestane steroid ring system featuring a hydroxyl group at the C-7 position (7α-hydroxy) and a sulfate group at the C-24 position (24R-sulfate). The polyamine spermine is conjugated to this steroid moiety at the C-3 position via a 3β-amino linkage.[2] This structural architecture bears resemblance to another marine-derived aminosterol, squalamine, which differs by incorporating a spermidine moiety instead of spermine.[2]

• IUPAC Name (free base): (3R,6R)-6-((3S,5R,7R,8R,9S,10S,13R,14S,17R)-3-((3-((4-((3-aminopropyl)amino)butyl)amino)propyl)amino)-7-hydroxy-10,13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)-2-methylheptan-3-yl hydrogen sulfate.[3]
• **IUPAC Name (trihydrochloride salt):**propylamino]-7-hydroxy-10,13-dimethyl-2,3,4,5,6,7,8,9,11,12,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-17-yl]-2-methylheptan-3-yl] hydrogen sulfate;trihydrochloride.[16]
• SMILES (free base example): CC@H[C@H]1CC[C@@H]2[C@@]1(CC[C@H]3[C@H]2C@@HO)C [3]
• InChIKey (free base example): WUJVPODXELZABP-FWJXURDUSA-N [3]
• InChIKey (trihydrochloride salt): DJYRGAKPWPDNTA-YPRMBGODSA-N [16]

The detailed structural information confirms Trodusquemine's classification as a complex aminosterol. The polyamine chain (spermine) conjugated to the steroid backbone is a critical feature that likely contributes to its unique biological activities and physicochemical properties. These include its interactions with biological membranes and its specific allosteric binding to PTP1B. The defined stereochemistry (e.g., 3β, 5α, 7α, 24R configurations) is essential for its precise interactions with biological targets.

C. Physicochemical Characteristics

The physicochemical properties of Trodusquemine (primarily for the free base, with some general properties) include:

Table 1: Key Chemical Identifiers and Physicochemical Properties of Trodusquemine (Free Base)

Property	Value	Source(s)
CAS Number (free base)	186139-09-3	1
Molecular Formula (free base)	C37​H72​N4​O5​S	3
Molecular Weight (free base)	685.066 g/mol	3
IUPAC Name (free base)	(3R,6R)-6-((3S,5R,7R,8R,9S,10S,13R,14S,17R)-3-((3-((4-((3-aminopropyl)amino)butyl)amino)propyl)amino)-7-hydroxy-10,13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)-2-methylheptan-3-yl hydrogen sulfate	3
SMILES (free base)	CC@H[C@H]1CC[C@@H]2[C@@]1(CC[C@H]3[C@H]2C@@HO)C	3
InChIKey (free base)	WUJVPODXELZABP-FWJXURDUSA-N	3
Water Solubility	0.000255 mg/mL (ALOGPS)	1
logP (octanol-water)	2.59 (ALOGPS), 2.93 (Chemaxon); 6.24 (InvivoChem)	1
pKa (Strongest Basic)	10.97 (Chemaxon)	1
Physiological Charge	+3 (Chemaxon)	1
Hydrogen Bond Donor Count	6 (Chemaxon & InvivoChem)	1
Hydrogen Bond Acceptor Count	8 (Chemaxon), 9 (InvivoChem)	1
Polar Surface Area (PSA)	145.94 Ų (Chemaxon)	1
Rotatable Bond Count	20 (Chemaxon & InvivoChem)	1
Rule of Five (Lipinski's)	No (Chemaxon)	1
Appearance	White to yellow solid powder	3
Solubility (General)	Soluble in DMSO	15
Storage (General)	Powder: -20°C for long term (3 years); 4°C for short term (2 years). In solvent: -80°C (6 months); -20°C (1 month)	3
Predicted Oral Bioavailability	0 (Chemaxon)	1

The physicochemical profile of Trodusquemine—characterized by very low water solubility, general lipophilicity (though logP values vary), a strongly basic nature due to the polyamine structure, and a physiological charge of +3—is typical of a complex natural product.[1] The high counts of hydrogen bond donors and acceptors, along with a significant number of rotatable bonds, suggest considerable conformational flexibility and potential for multiple intermolecular interactions.[1] These properties have profound implications for its formulation, routes of administration, and its absorption, distribution, metabolism, and excretion (ADME) profile.

The combination of a lipophilic steroid backbone with a highly charged polyamine tail (spermine, which carries a +3 charge at physiological pH [1]) results in an amphipathic molecule. This dual characteristic is likely fundamental to its membrane-interactive properties. Such properties are thought to enable its displacement of misfolded protein oligomers from cell membranes, a mechanism implicated in its neuroprotective effects.[19] Furthermore, this amphipathicity may also facilitate its allosteric interaction with PTP1B, which is anchored to the endoplasmic reticulum membrane.[4] The structural similarity to squalamine, another aminosterol known for its membrane interactions, further supports the importance of this characteristic.[2]

The computational prediction of zero oral bioavailability by Chemaxon [1] and the molecule's violation of Lipinski's Rule of Five (due to high molecular weight and hydrogen bond donor/acceptor counts [1]) strongly foreshadowed the clinical development challenges related to achieving adequate systemic exposure via oral administration. These challenges were indeed encountered for indications like obesity and type 2 diabetes.[4] This inherent limitation explains the predominant use of parenteral administration routes (e.g., intravenous in early clinical trials [22]) and the current development focus by Revidia Therapeutics on a subcutaneous formulation for Duchenne muscular dystrophy cardiomyopathy.[23] The positive charge at physiological pH will also significantly influence its interactions with biological membranes and its overall distribution within the body.

IV. Discovery, Natural Occurrence, and Synthesis

A. Isolation from Squalus acanthias (Spiny Dogfish Shark)

Trodusquemine is a naturally occurring cholestane derivative [3] that was first isolated from extracts of the liver of the spiny dogfish shark, Squalus acanthias.[2] Its discovery was an outcome of broader research initiatives aimed at identifying antimicrobial compounds in Squaliformes. These sharks are recognized for their robust innate immunity, which is thought to rely more on endogenous antimicrobial substances than on a highly developed adaptive immune system.[2] Squalamine, an aminosterol with structural similarities to Trodusquemine, was also identified through this line of investigation.[2] This origin underscores the marine environment as a rich and often untapped reservoir of novel bioactive compounds possessing unique chemical structures and potentially novel mechanisms of action. The initial focus on antimicrobial activity [2] highlights that the full therapeutic potential of a natural product may not be immediately apparent upon its discovery, with subsequent research often unveiling a wider array of pharmacological effects.

B. Synthetic Manufacturing Routes and Challenges

While Trodusquemine can be obtained through purification from its natural shark liver source, it is also amenable to synthetic manufacturing.[3] However, the synthetic process has been described as "fairly laborious" and one that requires "several weeks" to complete.[3] A comprehensive review of steroid polyamines indicates that the discovery of squalamine spurred extensive research into the total synthesis of related compounds, including Trodusquemine, often commencing from readily available cholic acids. The field has seen a proliferation of patent applications related to aminosterols, reflecting intense interest.[9] To illustrate the complexity involved, one reported synthesis of the related compound squalamine encompassed 17 steps and yielded a mere 0.3% overall.[9] Such intricate and low-yielding synthetic pathways can pose significant challenges for large-scale production and can heavily influence the cost of goods, both of which are critical considerations in pharmaceutical development.

The laborious nature of Trodusquemine's synthesis [3] and the potentially limited or variable supply from natural sources could have contributed to strategic decisions or a slower pace in its development pipeline. This is particularly relevant for broad therapeutic indications that would necessitate large quantities of the drug. Pharmaceutical development, especially for chronic conditions like obesity or type 2 diabetes, demands a substantial, consistent, and cost-effective drug supply. These potential supply chain and Cost Of Goods Sold (COGS) challenges might have influenced the original developer's capacity to sustain development or attract sufficient further investment, possibly contributing to the eventual discontinuation of efforts for metabolic indications.[18] The development of Claramine, a derivative reported to have a much simpler synthesis [3], points towards active efforts to circumvent these synthetic hurdles.

The structural similarity between Trodusquemine and squalamine [2], alongside their co-discovery context within the same research paradigm focusing on shark-derived antimicrobials [2], suggests the existence of a broader family of related aminosterols in sharks. These compounds may possess overlapping yet distinct biological activities. Trodusquemine features a spermine moiety, while squalamine incorporates spermidine [2]—a subtle structural variance that could significantly alter charge distribution, molecular flexibility, and target interaction profiles. Both compounds exhibit antimicrobial properties [2], and Trodusquemine is a well-characterized PTP1B inhibitor; squalamine also interacts with membranes and demonstrates diverse biological effects.[8] This commonality hints at a shared evolutionary origin or biosynthetic pathway in sharks for producing such defensive or regulatory molecules. Consequently, exploring other minor aminosterols from this natural source, or undertaking synthetic variations around this unique scaffold, could potentially yield new therapeutic leads with improved pharmacological or pharmacokinetic properties.

V. Mechanism of Action

A. Primary Target: Protein Tyrosine Phosphatase 1B (PTP1B) Inhibition

The principal and most extensively studied mechanism of action for Trodusquemine is its potent and highly selective inhibition of Protein Tyrosine Phosphatase 1B (PTP1B).[1] Trodusquemine functions as a non-competitive and allosteric inhibitor of PTP1B.[2] This means it binds to a site on the enzyme distinct from the catalytic active site [4], specifically targeting a novel allosteric binding pocket located within the C-terminal region of PTP1B.[4] The half-maximal inhibitory concentration (IC50​) value for Trodusquemine against PTP1B is consistently reported to be approximately 1 µM.[2]

A key feature of Trodusquemine is its significant selectivity for PTP1B over other phosphatases, including the closely related T-cell protein tyrosine phosphatase (TCPTP). Reports indicate a 150-fold to 200-fold preference for PTP1B, with an IC50​ for TCPTP around 224 µM.[18] Furthermore, it preferentially targets the full-length form of PTP1B (amino acids 1-405) more potently than truncated versions containing only the catalytic domain.[13] PTP1B itself is a non-receptor protein tyrosine phosphatase that is anchored to the cytoplasmic face of the endoplasmic reticulum (ER). It plays a crucial role as a negative regulator in multiple signaling pathways, most notably those концерты (concerts) by insulin and leptin, by dephosphorylating activated receptor tyrosine kinases (RTKs) and their downstream substrates.[4]

The allosteric and selective nature of Trodusquemine's PTP1B inhibition represents a significant advantage over many other PTP inhibitors. Historically, the development of direct, active-site PTP inhibitors has been fraught with challenges, primarily due to the highly conserved nature of the active sites among different PTP family members, leading to a lack of selectivity. Additionally, the positively charged nature of the phosphotyrosine-binding pocket often results in inhibitors with poor cell permeability and bioavailability.[4] Trodusquemine's unique allosteric mechanism of action offered a promising strategy to circumvent these common pitfalls, leading to its designation as a "first-in-class" PTP1B inhibitor.[3] This allosteric interaction, particularly with the full-length, ER-anchored form of PTP1B [4], is a sophisticated mode of inhibition that likely underpins its observed selectivity and potency in vivo. By binding to a region outside the conserved catalytic site, possibly influencing enzyme conformation or its interaction with substrates or regulatory partners at the ER membrane, Trodusquemine achieves a level of specificity that had been elusive for many orthosteric (active-site directed) inhibitors. This specific interaction with the native, membrane-associated form of PTP1B suggests that Trodusquemine might exploit unique structural features present only in this conformation, further enhancing its specificity within the cellular environment.

B. Impact on Insulin and Leptin Signaling Pathways

By effectively inhibiting PTP1B, Trodusquemine prevents the dephosphorylation of key components in the insulin signaling pathway, including the insulin receptor (IR) itself and its downstream substrates such as insulin receptor substrate-1 (IRS-1) and IRS-2.[2] This action leads to an enhancement of insulin signaling, an improvement in insulin sensitivity, and consequently, a reduction in blood glucose levels.[1] In cellular studies, such as those using HepG2 liver cells, MSI-1436 (at 10 µM) in conjunction with insulin was shown to significantly increase the phosphorylation of the insulin receptor β-subunit (p-IRβ).[15]

Similarly, PTP1B is a known negative regulator of the leptin signaling pathway, primarily through the dephosphorylation of Janus kinase 2 (JAK2), a critical kinase activated by the leptin receptor.[4] Trodusquemine's inhibition of PTP1B is therefore expected to enhance leptin sensitivity. This effect is believed to contribute significantly to its observed appetite-suppressing (anorexigenic) effects and its ability to promote weight loss.[1] The dual impact of Trodusquemine on both insulin signaling (which governs glucose homeostasis and peripheral energy metabolism) and leptin signaling (which controls central appetite regulation and energy expenditure) made it a particularly compelling therapeutic candidate for conditions like metabolic syndrome, type 2 diabetes, and obesity. This dual action was a central tenet of the early clinical development strategy pursued by Genaera Corporation.[22]

C. Blood-Brain Barrier Permeability and Central Nervous System Effects

A crucial pharmacological property of Trodusquemine is its ability to cross the blood-brain barrier (BBB).[3] This permeability allows it to exert direct effects within the central nervous system (CNS). These central actions are believed to be key to its appetite-suppressing effects, likely mediated by its influence on the paraventricular nucleus of the hypothalamus, a critical brain region for energy balance regulation.[1] Within the CNS, Trodusquemine has been shown to induce patterns of neuropeptide expression typically associated with weight loss, such as the downregulation of orexigenic (appetite-stimulating) neuropeptides like Agouti-related peptide (AgRP) and neuropeptide Y (NPY).[1] The capacity to penetrate the BBB is not only vital for its centrally-mediated anti-obesity effects but also underpins its potential utility in the treatment of various neurodegenerative diseases where central PTP1B activity or other targeted pathways are implicated.

D. Other Identified Molecular Targets

Beyond its primary action on PTP1B, Trodusquemine has been shown to interact with other molecular targets, although these are generally less emphasized in the literature compared to PTP1B inhibition. It demonstrates an affinity for and inhibitory action on the sodium-dependent dopamine transporter (DAT), with an IC50​ of 0.4 µmol/L, and the sodium-dependent norepinephrine transporter (NET), with an IC50​ of 0.7 µmol/L.[1] Inhibition of these transporters would lead to increased synaptic concentrations of dopamine and norepinephrine, respectively. Additionally, Trodusquemine has been suggested to act as an ion transport modulator.[1] These additional targets could contribute to its overall pharmacological profile, potentially influencing its effects on appetite, energy expenditure, mood (as suggested by its anxiolytic properties [2]), and perhaps some of its observed neuroprotective actions. However, the precise contribution of these secondary target interactions to the main therapeutic effects of Trodusquemine remains to be fully elucidated.

E. Membrane Interaction and Oligomer Displacement

A distinct and significant mechanism of action, particularly relevant to its potential in neurodegenerative diseases, is Trodusquemine's ability to interact with cell membranes and displace misfolded protein oligomers.[19] Studies have shown that Trodusquemine can markedly reduce the cytotoxicity of oligomeric forms of proteins such as α-synuclein (implicated in Parkinson's disease), amyloid-β (Aβ, implicated in Alzheimer's disease), and HypF-N by physically displacing these toxic oligomers from neuronal cell membranes. Notably, this protective effect can occur without inducing substantial morphological or structural changes in the oligomers themselves.[19] In the case of Aβ42, Trodusquemine has been reported to enhance its aggregation rate by accelerating secondary nucleation but, paradoxically, ameliorates the toxicity of the resulting oligomers by reducing their binding to cellular membranes.[20] This mechanism is proposed as a generic mode of neuroprotection against the common pathological threat posed by toxic protein oligomers in various proteinopathies.

This membrane-displacing activity against misfolded protein oligomers [19] appears to be a characteristic shared with its structural relative, squalamine.[20] Given Trodusquemine's amphipathic nature, arising from its lipophilic steroid core and cationic polyamine tail, this effect might be largely governed by direct physicochemical interactions with both the protein oligomers and the lipid components of the cell membrane. This could be a biophysical effect, potentially independent of specific receptor binding for this particular action. It is plausible that Trodusquemine alters membrane fluidity or surface charge, or directly binds to oligomers in a manner that prevents their deleterious insertion into or interaction with cell membranes. This raises an intriguing question: could this membrane-perturbing or oligomer-displacing capability also contribute to its initially discovered antimicrobial activity (as many antimicrobial peptides act by disrupting bacterial membranes) or even influence the activity or accessibility of its primary target, PTP1B, which is itself an ER-membrane anchored protein?[4] Such a "membrane modulation" theme could potentially unify several of Trodusquemine's diverse observed biological effects.

The convergence of these mechanisms—PTP1B inhibition (both central and peripheral), modulation of neurotransmitter transporters [1], and direct membrane-protective effects against toxic oligomers [19]—creates a powerful, multi-modal therapeutic agent. This confluence likely explains its exceptionally broad preclinical efficacy across a range of seemingly disparate conditions, including metabolic disorders, neurodegeneration, and processes involving tissue regeneration. Trodusquemine is thus more than just a "PTP1B inhibitor"; it acts as a complex biological response modifier.

VI. Preclinical Pharmacology and Therapeutic Potential

Trodusquemine (MSI-1436) has demonstrated a remarkably broad range of pharmacological activities in numerous preclinical models, highlighting its potential across various therapeutic areas.

A. Metabolic Disorders

1. Obesity and Appetite Suppression:

Trodusquemine has shown significant anti-obesity effects. It acts both centrally, likely via the hypothalamus, and peripherally to suppress feeding, prevent the reduction in energy expenditure often seen with caloric restriction, and induce patterns of neuropeptide expression typically associated with weight loss.1 Preclinical studies in various animal models, including diet-induced obese (DIO) mice, genetically obese (ob/ob), and diabetic (db/db) mice, have consistently demonstrated that Trodusquemine administration leads to sustainable, fat-specific weight loss without a concomitant reduction in lean muscle mass.2 This is accompanied by a reduction in adipocyte size and overall lipid content.22 An important observation is that Trodusquemine appears to overcome the metabolic readjustment (adaptive thermogenesis) that often limits the long-term efficacy of weight loss interventions based solely on caloric restriction.22 For instance, Lantz et al. (2010) reported that MSI-1436 administered at 10 mg/kg via intraperitoneal (i.p.) injection caused significant fat-specific weight loss in DIO mice.27 These compelling findings were a primary driver for Genaera Corporation's initial clinical trials targeting obesity.10 The specificity for fat loss is a highly desirable characteristic for an anti-obesity therapeutic.

2. Type 2 Diabetes and Glycemic Control:

In parallel with its anti-obesity effects, Trodusquemine exhibits potent anti-diabetic properties. It enhances insulin sensitivity and improves glucose tolerance through both central and peripheral mechanisms.1 Treatment with Trodusquemine has been shown to lower plasma insulin levels in DIO mice and improve fasting blood glucose levels in various hyperglycemic animal models.10 Mechanistically, it significantly enhanced insulin-stimulated tyrosine phosphorylation of the insulin receptor β-subunit (IRβ) and Signal Transducer and Activator of Transcription 3 (STAT3), direct targets of PTP1B, in HepG2 liver cells in vitro and/or in hypothalamic tissue in vivo.15 Given that PTP1B is a well-validated therapeutic target for type 2 diabetes, Trodusquemine's ability to concurrently improve insulin sensitivity and reduce body weight made it a particularly attractive candidate for this indication.

3. Hepatic Steatosis and Equine Metabolic Syndrome (EMS):

The metabolic benefits of Trodusquemine extend to liver health. It has been shown to correct hepatic steatosis (fatty liver disease) in ob/ob mice.2 Furthermore, intriguing research has emerged in the context of Equine Metabolic Syndrome (EMS), a condition in horses sharing similarities with human metabolic syndrome. In EMS-affected horses, MSI-1436 was found to ameliorate liver insulin sensitivity by modulating critical cellular pathways including autophagy, endoplasmic reticulum (ER) stress, and systemic inflammation.2 It also improves glucose uptake in the EMS-affected liver, an effect attributed to its anti-inflammatory and antifibrotic activities, and its ability to augment the levels of glycosylated glucose transporter 2 (Glut-2).31

Studies on insulin-resistant equine hepatic progenitor cells (HPCs) subjected to lipotoxic conditions (e.g., palmitate-induced stress) revealed that MSI-1436 promotes HPC entry into the cell cycle, protects them from apoptosis, increases glucose uptake (partially by increasing SIRT1 expression, a protein associated with liver insulin sensitivity), and crucially, restores mitochondrial dynamics and biogenesis. This includes modulation of key mitochondrial proteins such as PINK1, MFN1, and MFN2.21 These findings broaden the potential metabolic applications of Trodusquemine beyond human obesity and type 2 diabetes to related conditions like non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH), and even into veterinary medicine, showcasing the fundamental role of PTP1B in hepatic metabolism and cellular health.

B. Cardiovascular Applications

1. Atherosclerosis Reversal:

Trodusquemine has demonstrated potential in mitigating atherosclerosis. Preclinical studies in LDLR knockout (LDLR−/−) mice, a model for familial hypercholesterolemia and atherosclerosis, showed that Trodusquemine treatment can reverse atherosclerotic plaque development.2 Pharmacological inhibition of PTP1B with Trodusquemine was reported to protect against atherosclerotic plaque formation, reduce serum cholesterol and triglyceride levels in these mice fed a high-fat diet.2 Interestingly, these anti-atherosclerotic effects might involve mechanisms independent of direct insulin receptor phosphorylation in aortic tissue, possibly occurring via the phosphorylation and activation of AMP-activated protein kinase α (AMPKα) and Akt.6 Cardiovascular disease is a major comorbidity of metabolic disorders, and Trodusquemine's potential to address both the underlying metabolic dysregulation and direct vascular pathologies is of significant therapeutic interest.

2. Cardiac Tissue Regeneration and Myocardial Infarction (MI):

One of the most striking preclinical findings for Trodusquemine is its ability to stimulate the regeneration of heart tissue. This has been observed in adult zebrafish, a model organism known for its regenerative capacity, and more importantly, in adult mice, which have very limited intrinsic ability to repair heart damage.1 Following experimentally induced myocardial infarction (MI) in adult mice, intraperitoneal administration of MSI-1436 led to increased survival rates, improved heart function (as measured by ejection fraction and fractional shortening), a reduction in infarct size, diminished ventricular wall thinning, and an increase in cardiomyocyte proliferation in the damaged area.11 Significantly, the doses of MSI-1436 found to be effective in stimulating cardiac regeneration are reported to be 5 to 50 times lower than the maximum well-tolerated human dose identified in earlier metabolic trials.11 This remarkable regenerative capacity, particularly in the mammalian heart, is a key focus of current development efforts by Revidia Therapeutics for Duchenne muscular dystrophy-associated cardiomyopathy.23

3. Calcific Aortic Valve Disease (CAVD):

PTP1B expression has been found to be increased in calcific aortic valve disease (CAVD), a progressive condition characterized by thickening and calcification of aortic valve leaflets.2 Preclinical research indicates that MSI-1436 can alleviate aortic valve fibro-calcification and stenosis in a diet-induced mouse model of CAVD. This protective effect is associated with improved mitochondrial dynamics (through regulation of OPA1 homeostasis) and a reduction in the osteogenic differentiation of valvular interstitial cells (VICs), the primary cell type involved in valve pathology.2 Given the limited pharmacological treatment options for CAVD, PTP1B inhibition with agents like Trodusquemine presents a novel therapeutic strategy.

C. Neurobiology and Neurodegenerative Diseases

1. Neuroprotective Effects (Alzheimer's and Parkinson's Models):

Trodusquemine has shown considerable promise in preclinical models of neurodegenerative diseases. In mouse models of Alzheimer's disease (AD), it has been reported to reverse memory impairment, normalize behavior, reduce neuronal loss, and increase both healthspan and lifespan.2 More specifically, pharmacological inhibition of PTP1B with Trodusquemine was shown to rescue motor learning deficits, reduce neuroinflammation, and improve hyperglycemia in the PLB4 mouse model, which exhibits co-morbidities of AD and type 2 diabetes due to neuronal human BACE1 knock-in. In these mice, Trodusquemine treatment led to lower levels of amyloid precursor protein (APP), reduced astrogliosis, restoration of the endoplasmic reticulum chaperone BiP (Binding Immunoglobulin Protein), and decreased levels of IRS1 and dipeptidyl peptidase-4 (DPP4) in brain and liver tissue.10

In a C. elegans model of Parkinson's disease (PD), Trodusquemine reduced α-synuclein aggregation and increased healthspan and lifespan.2 It is listed among natural alkaloids active against synucleinopathies.10 A key mechanism underlying these neuroprotective effects is its ability to displace misfolded protein oligomers (such as α-synuclein and Aβ) from cell membranes, thereby abrogating their cytotoxicity.19 This dual mechanism—PTP1B inhibition (implicated in neuroinflammation and neuronal dysfunction) and direct anti-oligomer activity—makes Trodusquemine particularly interesting for complex neurodegenerative diseases where metabolic dysfunction and protein aggregation pathology are often intertwined.

2. Anxiolytic Properties:

Trodusquemine has also been reported to exert anxiolytic (anxiety-reducing) effects. This action is believed to be mediated by the restoration of endocannabinoid (eCB) signaling within the amygdala, a brain region critical for processing emotions like fear and anxiety.3 This suggests potential applications in anxiety disorders, possibly linked to its ability to cross the BBB and modulate central PTP1B activity or other relevant neurotransmitter systems.

D. Oncology

Trodusquemine has exhibited antitumor and antiangiogenic activities in various preclinical models.2 The inhibition of PTP1B by Trodusquemine can lead to a reduction in tumor cell proliferation in susceptible cancer cell types.3 PTP1B is known to be upregulated in certain types of cancer, such as HER2-driven breast cancers, where its increased expression is correlated with poor prognosis and increased metastatic potential.5

Specifically, MSI-1436 was shown to antagonize HER2 signaling, inhibit tumorigenesis in xenograft models, and abrogate metastasis in the NDL2 mouse model of HER2-positive breast cancer.13 These findings provided the rationale for the Phase 1 clinical trial (NCT02524951) in patients with metastatic breast cancer.13 Furthermore, recent drug sensitivity tests have suggested that MSI-1436 can suppress tumor cell viability and may enhance the efficacy of PD-1 inhibitors, a class of cancer immunotherapy drugs.31 This is consistent with findings that PTP1B can act as an intracellular checkpoint that limits T-cell and CAR T-cell antitumor immunity.2 The role of PTP1B in cancer is multifaceted, involving direct effects on tumor cell proliferation and survival, as well as modulation of the tumor microenvironment and anti-tumor immune responses.

E. Broad Regenerative Capabilities

Beyond cardiac regeneration, Trodusquemine has demonstrated a broader capacity to stimulate tissue repair. It promotes the regeneration of the amputated tail-fin in zebrafish, a complex structure comprising bone, connective tissue, skin, vasculature, and nerves.[2] In mammals, it stimulates the activation and proliferation of satellite cells, which are muscle stem cells crucial for the regeneration of injured skeletal muscle in mice.[11] The ability of Trodusquemine to stimulate regeneration across multiple, diverse tissues (heart, fin, skeletal muscle) and in different species (zebrafish, mice) suggests that PTP1B inhibition by this compound taps into fundamental and evolutionarily conserved endogenous repair mechanisms.[1] This broad regenerative potential is arguably one of Trodusquemine's most unique and compelling attributes and is the driving force behind its current development for DMD-associated cardiomyopathy.[23]

F. Antimicrobial and Geroprotective Properties

Trodusquemine was initially discovered through a search for antimicrobial compounds and indeed exhibits broad-spectrum antimicrobial activity.[2] Additionally, some research suggests that Trodusquemine may function as a novel endogenous vertebrate geroprotector, a compound that targets fundamental aging-associated processes at both cellular and in vivo levels, potentially promoting healthspan.[2] While these properties have been less explored in its later clinical development pathway compared to its metabolic and regenerative effects, they contribute to the complex biological profile of this multifaceted molecule and hint at potential roles in innate immunity and the biology of aging.

Table 2: Summary of Preclinical Pharmacological Effects and Therapeutic Potential of Trodusquemine

Therapeutic Area	Specific Effect/Model	Key Findings	Key Source(s)
Metabolic Disorders	Obesity/Appetite Suppression (DIO, ob/ob, db/db mice)	Suppresses feeding, fat-specific weight loss, reduces adipocyte size, overcomes metabolic readjustment.	1
	Type 2 Diabetes/Glycemic Control (DIO, hyperglycemic mice, HepG2 cells)	Enhances insulin sensitivity, improves glucose tolerance, lowers plasma insulin, increases p-IRβ.	1
	Hepatic Steatosis (ob/ob mice) / Equine Metabolic Syndrome (horses, equine HPCs)	Corrects hepatic steatosis; ameliorates liver insulin sensitivity, modulates autophagy, ER stress, inflammation, restores mitochondrial dynamics in EMS models.	2
Cardiovascular	Atherosclerosis (LDLR-/- mice)	Reverses/protects against plaque formation, reduces serum cholesterol/triglycerides, may involve AMPKα/Akt.	2
	Cardiac Regeneration/Myocardial Infarction (zebrafish, mice)	Increases survival, improves heart function, reduces infarct size, increases cardiomyocyte proliferation at low doses.	1
	Calcific Aortic Valve Disease (mouse model)	Alleviates aortic valve fibro-calcification/stenosis, improves mitochondrial dynamics, reduces VIC osteogenic differentiation.	2
Neurobiology	Neuroprotection (Alzheimer's/Parkinson's models - mice, C. elegans)	Reverses memory impairment, reduces neuronal loss, reduces α-syn/Aβ oligomer toxicity by membrane displacement; rescues AD/T2DM comorbidity phenotypes in BACE1 model.	2
	Anxiolytic Effects (mice)	Restores endocannabinoid signaling in amygdala.	3
Oncology	Antitumor/Antiangiogenic (various models, HER2+ breast cancer)	Reduces tumor cell proliferation, antagonizes HER2 signaling, inhibits tumorigenesis/metastasis, may enhance PD-1 inhibitor efficacy.	2
Regeneration	Broad Tissue Regeneration (zebrafish tail-fin, mouse skeletal muscle)	Stimulates regeneration of fin tissue, activates satellite cells in muscle.	2
Other	Antimicrobial Activity	Broad-spectrum antimicrobial effects.	2
	Geroprotective Effects	Suggested as a novel endogenous vertebrate geroprotector.	2

The astonishingly broad range of Trodusquemine's preclinical efficacy across diverse organ systems and disease models strongly suggests that its primary target, PTP1B, functions as a critical homeostatic regulator and a key node in numerous pathological processes. PTP1B negatively regulates fundamental pathways like insulin and leptin signaling [4]; it is implicated in ER stress, inflammation, and apoptosis [2]—processes common to many chronic diseases. Its inhibition by Trodusquemine promotes tissue regeneration [1], indicating that PTP1B normally constrains endogenous repair mechanisms. Furthermore, PTP1B is involved in neuronal function, neuroinflammation [2], cancer cell signaling, and immune responses.[2] The fact that a single molecule, primarily targeting one enzyme, can elicit such widespread beneficial effects points to the central importance of PTP1B in maintaining health and its dysregulation in disease. Inhibition of PTP1B by Trodusquemine appears to effectively "release the brakes" on multiple beneficial cellular programs.

A crucial observation is that the doses of Trodusquemine effective for stimulating tissue regeneration are reported to be 5 to 50 times lower than the maximum well-tolerated human dose observed in earlier metabolic trials.[11] This suggests potentially different therapeutic windows and perhaps different degrees or sites of PTP1B engagement required for regenerative versus systemic metabolic effects. Metabolic outcomes like weight loss or global glucose control might necessitate more profound or sustained PTP1B inhibition in specific key tissues such as the liver and hypothalamus. In contrast, regenerative effects might be triggered by a more subtle or localized modulation of PTP1B activity within injured tissues, sufficient to activate repair pathways without inducing the systemic metabolic shifts that appear to require higher doses. This dose differentiation could be pivotal for its current development in DMD cardiomyopathy [23], where a lower, potentially safer dose might still achieve significant cardiac benefit, possibly mitigating side effects or pharmacokinetic challenges encountered at the higher doses previously explored for obesity.

Despite its outstanding and broad preclinical success, Trodusquemine faced significant hurdles in clinical translation, particularly for metabolic diseases, which led to the discontinuation of its development for these indications by Genaera Corporation.[4] This situation highlights the common and often frustrating "bench-to-bedside" gap in drug development. The reasons for these challenges appear to be multifactorial, including pharmacokinetic issues related to bioavailability in humans (particularly for oral administration) [4], and the financial instability of the developing company.[2] Animal models, while invaluable for discovery and mechanistic understanding, do not always accurately predict human physiological responses or drug pharmacokinetics. The inherent physicochemical properties of Trodusquemine [1] already hinted at potential bioavailability challenges. Moreover, drug development is a high-risk, capital-intensive endeavor, making the viability and continuity of the sponsoring company a critical factor. This pattern emphasizes that even with a compelling mechanism of action and robust preclinical data, clinical success is not guaranteed. The subsequent efforts by companies like DepYmed [14] and Revidia Therapeutics [23] to continue Trodusquemine's development demonstrate persistent belief in the molecule's therapeutic value, albeit with adjusted strategies focusing on different indications, formulations, or patient populations.

VII. Pharmacokinetics (ADME)

A. Absorption, Distribution, Metabolism, and Excretion (ADME) Overview

Detailed human ADME (Absorption, Distribution, Metabolism, and Excretion) data for Trodusquemine are not extensively available in the provided information. However, preclinical ADME studies formed part of the IND-enabling work conducted by Revidia Therapeutics for its development in Duchenne Muscular Dystrophy (DMD) cardiomyopathy.[23]

A computational prediction by Chemaxon suggests that the oral bioavailability of Trodusquemine is effectively zero.[1] This prediction aligns with reports from clinical development, where poor bioavailability in patients was cited as a reason for discontinuing trials for metabolic indications [4], and with general concerns about the challenges of oral administration for this molecule.[18] Trodusquemine is reported to be soluble in dimethyl sulfoxide (DMSO) [15], a common solvent for compounds with low aqueous solubility.

A significant distributional characteristic is Trodusquemine's ability to cross the blood-brain barrier (BBB).[3] This is crucial for its centrally-mediated effects on appetite and its potential in treating CNS disorders.

Regarding administration routes, preclinical studies in diet-induced obese mice often utilized intraperitoneal (i.p.) injections.[3] Early clinical trials for obesity and type 2 diabetes employed intravenous (IV) administration.[10] More recently, Revidia Therapeutics is developing a subcutaneous (SC) formulation for the treatment of DMD cardiomyopathy.[23]

The limited specific ADME data for Trodusquemine itself represents a gap in the publicly available information. The consistent theme emerging from predictions and clinical experience is the challenge associated with oral bioavailability, which has necessitated the exploration and use of alternative administration routes throughout its research and development history.

B. Bioavailability and Blood-Brain Barrier Penetration

Oral Bioavailability: As noted, oral bioavailability is predicted to be very low [1] and proved to be problematic in human clinical trials for metabolic indications, contributing to their discontinuation.[4] This difficulty in achieving adequate systemic exposure via the oral route was a major impediment. Efforts to address this led to the development of analogs like DPM-1001, which was specifically designed to be orally bioavailable.[4]

Blood-Brain Barrier (BBB) Penetration: Trodusquemine is confirmed to cross the BBB when administered systemically via non-oral routes.[3] This characteristic is essential for its centrally-mediated effects, such as appetite suppression via hypothalamic PTP1B inhibition [1], and underpins its investigational potential for treating neurodegenerative diseases where central targets are involved.[2]

The dichotomy between poor oral bioavailability and effective BBB penetration (when administered parenterally) is an important aspect of Trodusquemine's pharmacokinetic profile. While oral delivery for chronic systemic diseases like obesity and type 2 diabetes proved to be a major hurdle, its ability to reach the brain supports continued investigation for CNS disorders or conditions where central PTP1B inhibition is a key therapeutic mechanism.

The poor oral bioavailability of Trodusquemine, as predicted computationally [1] and observed clinically for metabolic indications [4], likely served as a critical limiting factor—an "Achilles' heel"—for its development in mass-market indications such as obesity and type 2 diabetes. These conditions typically favor oral medications for chronic use to ensure patient compliance and market viability. This significant pharmacokinetic limitation appears to have directly prompted the strategic pivot by subsequent developers, notably Revidia Therapeutics. Revidia's focus on an orphan disease, DMD cardiomyopathy [23], and the development of an alternative delivery route (subcutaneous formulation [23]) represent a pragmatic approach. Orphan diseases often allow for less convenient administration routes if a significant unmet medical need is addressed, and the effective doses for regeneration are reported to be lower than those for metabolic effects [11], potentially easing the delivery challenge. This strategic shift explicitly acknowledges and attempts to bypass the oral PK limitation by targeting a different patient population with distinct therapeutic expectations.

The inherent physicochemical properties of Trodusquemine—such as its high molecular weight, multiple hydrogen bond donors and acceptors, and the charged polyamine moiety [1]—are intrinsically challenging for efficient oral absorption and membrane permeation, explaining its violation of Lipinski's Rule of Five.[1] The successful development of DPM-1001, an analog with improved oral bioavailability [4], demonstrates that the core pharmacophore responsible for PTP1B inhibition can be chemically modified to enhance "drug-like" pharmacokinetic properties without sacrificing activity. DPM-1001 involved modifications to the polyamine tail and the C-24 sulfate group [13], suggesting these regions were key contributors to Trodusquemine's poor oral PK. The fact that DPM-1001 retains PTP1B inhibitory activity [4] indicates that the core steroid structure and its general mode of interaction with the allosteric site can tolerate such chemical alterations. This highlights a potential path forward: if Trodusquemine's broad efficacy is desired alongside oral administration, further medicinal chemistry efforts focusing on its scaffold, drawing lessons from DPM-1001, could prove fruitful. It also implies that the PTP1B target itself continues to be regarded as highly valuable for therapeutic intervention.

VIII. Clinical Development and Trials

A. Early Phase Trials in Metabolic Disorders (Primarily by Genaera Corp.)

Genaera Corporation spearheaded the initial clinical development of Trodusquemine for metabolic disorders.

• Study MSI-1436C-101: This was a Phase 1, double-blind, randomized, placebo-controlled, single ascending intravenous (IV) dose study conducted in healthy overweight or obese volunteers (Body Mass Index 27-40 kg/m²). Data were presented in October 2007.[22]
• NCT00606112 (Study MSI-1436C-103): This Phase 1 trial, also sponsored by Genaera, was a double-blind, randomized, placebo-controlled, ascending IV single-dose study in obese individuals with Type 2 Diabetes. It aimed to evaluate pharmacokinetics (PK), safety, and short-term indices of glucose control.[10]
• NCT00806338: This was a Phase 1, double-blind, randomized, placebo-controlled study assessing ascending IV multiple doses of Trodusquemine in obese or overweight volunteers with Type 2 Diabetes.[10]
• NCT00509132: This identifier is also mentioned in connection with Phase 1 trials by Genaera examining tolerability and PK in individuals with obesity and/or Type 2 diabetes.[18]

Key findings from these early trials indicated that Trodusquemine, when administered intravenously, was generally well-tolerated at doses considered likely to be clinically relevant.[11] No serious adverse events were reported in the MSI-1436C-101 study.[22] Nausea was identified as a dose-limiting toxicity in this study, with a maximum tolerated single dose (MTD) established at 40 mg/m².[22] The pharmacokinetic profile of IV Trodusquemine showed a consistent pattern with minimal subject-to-subject variability and linearity across the dose ranges studied in MSI-1436C-101.[22] Furthermore, improvements in glucose tolerance were observed [18], and the data supported the proposed PTP1B inhibition mechanism in vivo.[11]

Despite these initially promising Phase 1 results with IV administration, the development of Trodusquemine for metabolic indications was ultimately halted. A primary factor was the financial collapse of Genaera Corporation, which filed for liquidation in 2009.[18] Beyond the sponsor's demise, Trodusquemine was later reported to have been discontinued for these human clinical trials due to challenges with low activity and, crucially, poor bioavailability in patients when considering practical long-term administration routes.[4] It was also noted that the full results of these early trials were not always published in peer-reviewed literature.[18] The transition to later-phase studies, which would ideally involve an oral formulation for chronic metabolic diseases, likely encountered insurmountable bioavailability and efficacy hurdles that, compounded by Genaera's financial difficulties, led to the cessation of this development arm.

B. Oncology Trials (Metastatic Breast Cancer)

Trodusquemine (as MSI-1436C) was also investigated for its potential in oncology.

• Study NCT02524951: This was "A Phase I Study of the Safety and Tolerability of Single Agent MSI-1436C in Metastatic Breast Cancer Patients".[10]
• The trial was listed as sponsored by Northwell Health.[37] DepYmed, Inc. was actively conducting this trial with MSI-1436C at Northwell Health's Monter Cancer Center, focusing on HER2-positive breast cancer.[14] Funding for related PTP1B research in breast cancer was also acknowledged from organizations such as Susan G. Komen and the Breast Cancer Research Foundation.[37]
• The status of this trial is reported as "Terminated".[10]
• The specific reason for the termination of NCT02524951 is not explicitly stated within the provided research materials. While general statements mention that some Phase II trials of Trodusquemine were halted due to "financial difficulties of the developer" [2], it is unclear if this directly applies to DepYmed and this specific Phase 1 oncology trial. Other possibilities for termination could include insufficient efficacy, safety concerns, or strategic decisions by the sponsor. The available snippets do not provide a definitive reason for the termination of this particular trial.

The rationale for investigating Trodusquemine in oncology, particularly HER2-positive breast cancer, stemmed from the understanding of PTP1B's role in promoting HER2-driven cancer progression and MSI-1436's preclinical efficacy in relevant breast cancer models.[5] The termination of this trial without a clearly documented public reason (within these materials) leaves its potential in this specific oncology setting uncertain.

C. Orphan Drug Designation for Dystrophinopathies

A significant recent development in Trodusquemine's journey is its recognition for a rare disease indication. Trodusquemine HCl received Orphan Drug Designation from the U.S. Food and Drug Administration (FDA) on February 19, 2021, for the "Treatment of Dystrophinopathies".[12] The sponsor holding this designation is Revidia Therapeutics, Inc..[12] It is important to note that while designated, Trodusquemine is not yet FDA-approved for this orphan indication.[12] This designation is a crucial regulatory milestone, offering various incentives to support the development of treatments for rare diseases. It reflects the promising preclinical data on Trodusquemine's regenerative capabilities, especially concerning muscle and heart tissue, which are directly relevant to the pathology of Duchenne Muscular Dystrophy (DMD) and its associated cardiomyopathy.[23]

Table 3: Summary of Key Clinical Trials for Trodusquemine (MSI-1436)

ClinicalTrial.gov ID / Study ID	Phase	Indication(s)	Sponsor(s)/Developer(s)	Admin. Route	Status	Key Reported Outcomes/Endpoints	Notes/Reason for Discontinuation (if available)
MSI-1436C-101	1	Obesity (Healthy Overweight/Obese)	Genaera Corp.	IV	Completed	Well-tolerated, no SAEs, consistent PK, MTD 40 mg/m² (nausea dose-limiting).	Development halted due to Genaera liquidation & later reports of low activity/bioavailability in patients for metabolic indications.
NCT00606112 (MSI-1436C-103)	1	Obesity & Type 2 Diabetes	Genaera Corp.	IV	Completed	PK, safety, short-term glucose control. Improved glucose tolerance reported.	Same as above. Full results not always published.
NCT00806338	1	Obesity & Type 2 Diabetes (Multiple Dose)	Genaera Corp.	IV	Completed	Safety, PK, tolerability.	Same as above.
NCT00509132	1	Obesity & Type 2 Diabetes	Genaera Corp.	IV	Completed (assumed)	Tolerability, PK.	Same as above.
NCT02524951	1	Metastatic Breast Cancer (HER2-positive focus)	Northwell Health / DepYmed, Inc.	IV (assumed)	Terminated	Safety and tolerability of MSI-1436C.	Reason for termination not explicitly stated in provided materials.

The pursuit of an orphan drug designation for Dystrophinopathies by Revidia Therapeutics [12] exemplifies a common and often astute strategic pivot for drug candidates that have demonstrated broad preclinical promise but encountered significant challenges (e.g., pharmacokinetic limitations, sponsor instability) in larger, more common indications. Orphan indications typically involve smaller, more genetically or phenotypically homogeneous patient populations, may have different efficacy endpoints more readily achievable, and often benefit from greater regulatory flexibility and support. Furthermore, the burden of less convenient administration routes (like subcutaneous injection) or the acceptance of certain side effect profiles might be different in the context of severe, life-limiting orphan diseases with few or no existing effective treatments. This strategic shift suggests a "repurposing" or "re-focusing" effort to salvage a molecule with inherent biological value by targeting an area of high unmet medical need where its specific strengths (e.g., regenerative effects at potentially lower doses [11]) can be optimally leveraged.

The clinical development history of Trodusquemine is also marked by changes in sponsorship and the financial failure of at least one key developer, Genaera Corporation.[18] This underscores a critical reality in pharmaceutical development: scientific merit and compelling preclinical data alone are insufficient for success. The financial health, strategic vision, and operational continuity of the sponsoring entity are paramount for navigating the long, complex, and expensive journey from bench to bedside. The fragmented development history, with rights passing between entities [12], can lead to a loss of development momentum, potential data gaps, and challenges in constructing and executing a cohesive long-term strategy.

Finally, the lack of detailed, publicly available results for some of the completed or terminated trials, such as the full data from Genaera's Phase 1 metabolic studies [18] or a clear, publicly documented reason for the termination of the NCT02524951 oncology trial, represents a common issue in drug development often referred to as "data darkness." Companies are not always obligated to publish comprehensive results of early-phase or terminated trials, particularly if the outcomes are negative or strategically sensitive. This lack of transparency can hinder the broader scientific community's ability to learn collectively from both successes and failures, potentially leading to redundant research efforts or missed opportunities for understanding why a drug may have failed for a particular indication or in a specific patient population.

IX. Development History and Current Investigational Status

A. Key Corporate Entities Involved

The development of Trodusquemine has passed through several corporate hands:

• Genaera Corporation: Was the initial primary developer of Trodusquemine (MSI-1436). They advanced the compound through Phase 1 clinical trials for obesity and type 2 diabetes (studies MSI-1436C-101, NCT00606112, NCT00806338) in the mid to late 2000s.[10] However, Genaera Corporation announced a Plan of Complete Liquidation and Dissolution in April 2009 [24], having sold off its assets, which included Trodusquemine.[18]
• DepYmed Inc.: This company subsequently acquired rights to Trodusquemine (referred to as MSI-1436C). DepYmed was responsible for conducting a Phase 1 clinical trial (NCT02524951) investigating MSI-1436C as a therapeutic candidate for HER2-positive breast cancer, in collaboration with Northwell Health.[14] DepYmed also stated involvement in the preclinical development of more potent PTP1B inhibitors.[14]
• Northwell Health: Acted as the sponsor for the NCT02524951 trial in metastatic breast cancer [37], with the clinical study conducted at their Monter Cancer Center.[14]
• Revidia Therapeutics, Inc.: Currently appears to be the most active entity in Trodusquemine's development. Revidia is focusing on a novel subcutaneous formulation of MSI-1436 specifically for the treatment of Duchenne Muscular Dystrophy (DMD)-associated cardiomyopathy.[23] They are the holders of the FDA Orphan Drug Designation for Trodusquemine HCl for the "Treatment of Dystrophinopathies".[12] Revidia has reported completion of multiple IND-enabling workstreams and is progressing towards initiating clinical trials.[23]
• Novo Biosci: This name appears in a database entry as a source or developer associated with "trodulamine (MSI-1436)" in relation to recent preclinical research publications.[31] However, their specific role in the development or current rights to Trodusquemine is not detailed in the provided materials.
• Fountain Therapeutics / Navidea Biopharmaceuticals: While these names were part of the initial search scope or related queries, the provided snippets do not establish a clear, direct role for Fountain Therapeutics or Navidea Biopharmaceuticals in the clinical development of Trodusquemine itself. For instance, [10], which were retrieved in relation to Fountain Therapeutics and trial termination reasons, discuss a different breast cancer trial (ZEST, involving niraparib) and do not link Fountain to Trodusquemine or NCT02524951. Similarly, information on Navidea primarily pertains to its Manocept platform [39], and vendor pages listing MSI-1436 [27] do not indicate active development by Navidea.

B. Development of Analogs

Recognizing some of the limitations of Trodusquemine, particularly its challenging synthesis and poor oral bioavailability, efforts have been made to develop analogs:

• DPM-1001: This is an analog of Trodusquemine (MSI-1436) in which the spermine tail at the C-3 position was replaced with a pyridin-2-ylmethyl-amino-butyl-amine group, and the sulfate group at C-24 was replaced with a methyl ester.[13] DPM-1001 was identified as a potent and specific inhibitor of PTP1B with the significant advantage of being orally bioavailable.[4] An interesting additional property is its ability to chelate copper, which reportedly enhances its PTP1B inhibitory potency.[13] In preclinical models (high-fat diet-fed mice), DPM-1001 demonstrated efficacy in reversing obesity and improving insulin sensitivity.[4] Notably, DPM-1001 received FDA Orphan Drug Designation in May 2022 for the treatment of Wilson Disease, a genetic disorder of copper metabolism.[4]
• Claramine: Described as a novel polyaminosteroid derivative containing a spermino group, similar to Trodusquemine. A key advantage reported for Claramine is its significantly easier and more rapid synthesis (2 days compared to several weeks for Trodusquemine). It also displayed selective inhibition of PTP1B (but not the closely related TC-PTP) and, in cultured neuronal cells, activated key components of insulin signaling in a manner similar to Trodusquemine.[3]

The development of these analogs signifies ongoing efforts within the scientific community to harness the therapeutic potential of PTP1B inhibition while addressing the pharmaceutical liabilities of the parent compound, Trodusquemine. DPM-1001's progression to an orphan drug designation for Wilson Disease is particularly noteworthy, suggesting that chemical modifications can not only improve pharmacokinetics but also potentially unveil new therapeutic applications based on altered or additional properties (like copper chelation).

C. Current Focus: Duchenne Muscular Dystrophy (DMD) Cardiomyopathy (by Revidia Therapeutics)

The most prominent and active area of Trodusquemine's (MSI-1436) current clinical development is its investigation by Revidia Therapeutics for the treatment of cardiomyopathy associated with Duchenne Muscular Dystrophy (DMD).[23] Heart failure resulting from progressive dilated cardiomyopathy is the primary cause of mortality in patients with DMD.[23] Revidia is advancing a novel subcutaneous (SC) formulation of MSI-1436 for this indication.

Revidia's preclinical research has demonstrated that MSI-1436 stimulates heart muscle regeneration, improves heart function (e.g., left ventricle ejection fraction), and reduces infarct size in wild-type adult mice following myocardial infarction. Crucially, it has also shown efficacy in mouse models directly relevant to DMD, including the B10-Dmdmdx/J DMD mouse model and aged DMD animals, where it improved left ventricle ejection fraction.[23] A key finding supporting this focused development is that the doses of MSI-1436 that effectively reverse cardiac injury in these models are reported to be up to 50 times lower than the maximum well-tolerated human dose established in earlier clinical trials for metabolic diseases.[23]

Revidia Therapeutics has reported the completion of multiple IND-enabling workstreams. These include successful FDA pre-IND meetings, extensive efficacy testing in multiple animal models, in vitro safety pharmacology studies, ADME studies, dose-range finding experiments, chemistry, manufacturing, and controls (CMC) development, and Good Laboratory Practice (GLP) manufacturing of the drug substance.[23] The final IND-enabling step involves FDA-required GLP-compliant safety and toxicity testing of the subcutaneously administered MSI-1436. This includes repeat-dose toxicology studies, genotoxicity testing, and CNS, respiratory, and cardiovascular safety pharmacology assessments.[23] Revidia Therapeutics has stated a target for submitting an Investigational New Drug (IND) application in early 2025, with the goal of initiating clinical trials later that same year.[23] This focused effort on a severe orphan disease with a high unmet medical need, utilizing a different formulation and potentially a more favorable dosing regimen, represents the most promising current clinical path for Trodusquemine.

D. Recent Research (2023-2025)

Ongoing academic and preclinical research continues to explore the diverse biological activities and mechanisms of Trodusquemine (MSI-1436), with several notable findings emerging between 2023 and early 2025:

• Alzheimer's Disease (AD): Further studies have reinforced its potential in AD. Pharmacological PTP1B inhibition with Trodusquemine was shown to rescue motor learning deficits, mitigate neuroinflammation, and improve hyperglycemia in a BACE1 knock-in mouse model that exhibits AD and Type 2 Diabetes co-morbidities. Mechanistically, Trodusquemine treatment led to lower amyloid precursor protein (APP) levels, reduced astrogliosis, restoration of the ER chaperone BiP, and decreased levels of IRS1 and DPP4 in the brain and liver.[10]
• Equine Metabolic Syndrome (EMS): Research in veterinary models, specifically EMS, continues to highlight Trodusquemine's benefits. It has been shown to restore metabolic flexibility and mitochondrial dynamics in insulin-resistant equine hepatic progenitor cells (HPCs), improve glucose uptake, and exert anti-inflammatory and antifibrotic activity in the EMS-affected liver.[31] It also modulates autophagy, ER stress, and systemic inflammation in this context.[2]
• Cancer: In the realm of oncology, PTP1B inhibitor MSI-1436 demonstrated sensitivity in suppressing tumor cell viability and was suggested to enhance the efficacy of PD-1 checkpoint inhibitors.[31] This aligns with the growing understanding of PTP1B as an immune checkpoint.
• Mitochondrial Dynamics: A recurring theme in recent research is Trodusquemine's positive impact on mitochondrial health. It promotes mitochondrial dynamics by modulating mitochondrial quantity and morphotype, as well as the expression of key regulatory proteins like PINK1, MFN1, and MFN2, particularly observed in equine HPCs under metabolic stress.[21]
• Membrane Interactions: Investigations into Trodusquemine's influence on the organization of lipid rafts within neuronal membranes and its broader interactions with cell membranes continue, seeking to further elucidate this aspect of its mechanism.[31]

These recent studies reaffirm the diverse biological activities of Trodusquemine and continue to delve deeper into its underlying mechanisms of action. They frequently highlight mitochondrial health, inflammation, and ER stress as key modulatory points for its therapeutic effects, not only in established areas like neuroinflammation and metabolic liver disease (now extending to veterinary applications) but also in emerging fields like cancer immunotherapy.

Despite significant setbacks in its development history, including the failure of its initial sponsor (Genaera Corporation [18]) and the discontinuation of clinical trials for major metabolic indications [4] and an oncology indication (NCT02524951 [10]), Trodusquemine continues to attract research and development interest. This resilience, evidenced by the activities of companies like DepYmed [14] and more recently Revidia Therapeutics [23], alongside ongoing academic research [31], suggests a strong underlying scientific conviction in the therapeutic value of PTP1B inhibition and/or the unique properties of Trodusquemine itself. The breadth of compelling preclinical data across numerous disease models is difficult to ignore, and PTP1B remains a highly validated, albeit challenging, drug target.[4] Trodusquemine's allosteric mechanism of inhibition remains an attractive feature.[2] New companies have been willing to invest in navigating its known challenges, often by employing novel strategies such as targeting orphan indications, developing new formulations, or exploring its potential in combination therapies.

Trodusquemine's development trajectory illustrates an evolution in therapeutic strategy: an initial focus on broad metabolic markets (obesity and type 2 diabetes by Genaera [22]), followed by a more niche oncology attempt (HER2-positive breast cancer by DepYmed [14]), and now a highly specific orphan regenerative medicine application (DMD cardiomyopathy by Revidia [12]). Success in a well-defined orphan indication like DMD could, paradoxically, re-ignite interest in broader applications. If Revidia's efforts validate the drug's safety and efficacy in humans, particularly with a new formulation or at the lower doses proposed for regenerative effects, it could de-risk the exploration of Trodusquemine in other conditions where PTP1B modulation or tissue regeneration is beneficial (e.g., other muscular dystrophies, broader forms of heart failure, or even neurodegenerative diseases). Furthermore, the development of orally bioavailable analogs like DPM-1001 [4] keeps the door open for revisiting metabolic indications if the critical pharmacokinetic hurdles can be definitively overcome with next-generation compounds.

The journey of Trodusquemine, from its discovery related to antimicrobial properties in sharks (likely in the 1990s, given squalamine's discovery timeline [8]) to its active development for a rare genetic disorder in the 2020s [23], exemplifies the often protracted, complex, and winding path of natural product-derived drugs. The initial scientific excitement, followed by significant development challenges, and then a re-emergence with new strategies or for new indications, is a recurring theme in the pharmaceutical industry. This long timeline reflects the inherent complexities of understanding novel biological mechanisms, overcoming manufacturing and formulation challenges associated with complex natural products [3], navigating the rigors of clinical translation, and the profound impact of corporate stability and strategic continuity.

X. Discussion

Trodusquemine (MSI-1436) presents a fascinating case study in drug development, characterized by a unique confluence of natural product origin, a sophisticated molecular mechanism, broad preclinical efficacy, and a challenging journey through clinical translation. Its identity as a spermine metabolite of cholesterol, isolated from the spiny dogfish shark [1], immediately sets it apart. The primary mechanism, allosteric inhibition of PTP1B [2], targets a key negative regulator of insulin and leptin signaling, offering a strong rationale for its investigation in metabolic diseases. Furthermore, its ability to cross the blood-brain barrier [3] opened avenues for CNS applications, while its distinct capacity to displace misfolded protein oligomers from cell membranes [19] provided an additional, compelling mechanism for neuroprotection.

The preclinical data for Trodusquemine are remarkably extensive and positive across an array of conditions. It demonstrated significant potential in models of obesity, type 2 diabetes, hepatic steatosis, atherosclerosis, myocardial infarction, calcific aortic valve disease, Alzheimer's disease, Parkinson's disease, anxiety, and various cancers, alongside broad tissue regenerative capabilities in fin, heart, and skeletal muscle.[1] This breadth suggests that PTP1B is indeed a master regulator in many physiological and pathological states, and its inhibition by Trodusquemine can unlock multiple therapeutic benefits.

However, the transition from this impressive preclinical profile to successful clinical application for broad indications like obesity and type 2 diabetes was fraught with challenges. Pharmacokinetic hurdles, particularly the poor oral bioavailability of Trodusquemine [1], proved to be a major obstacle for chronic oral therapies. Compounding these scientific and technical difficulties was the financial instability of its initial developer, Genaera Corporation, which ultimately ceased operations.[18] The subsequent attempt to develop it for metastatic breast cancer by DepYmed and Northwell Health also did not lead to an approved product, with the Phase 1 trial being terminated.[10]

Despite these setbacks, the compelling biology of PTP1B and the unique properties of Trodusquemine have fueled continued interest. The current strategic repositioning by Revidia Therapeutics towards Duchenne muscular dystrophy-associated cardiomyopathy represents a more focused approach.[12] This strategy leverages Trodusquemine's potent regenerative effects, which are observed at doses significantly lower than those explored for metabolic disorders [11], and targets an orphan disease with high unmet medical need where non-oral formulations (subcutaneous) are more acceptable. This "orphan pivot" is a pragmatic way to potentially realize the value of a molecule that faced barriers in larger markets.

The development of analogs like DPM-1001, which exhibits improved oral bioavailability while retaining PTP1B inhibitory activity and even gaining new properties like copper chelation (leading to an orphan designation for Wilson Disease [4]), further underscores the enduring potential of this chemical scaffold. It suggests that the limitations of the parent molecule might be overcome through medicinal chemistry, potentially re-opening doors for indications that require oral administration.

Trodusquemine's story offers broader lessons for drug development. It highlights the immense therapeutic potential that can reside in natural products and the value of exploring unique biological niches. It also underscores the difficulties in drugging targets like phosphatases and the critical importance of favorable pharmacokinetics for clinical success, especially for chronic diseases. Finally, it demonstrates that the path from discovery to market can be long and tortuous, often requiring strategic flexibility, perseverance, and the evolution of therapeutic focus as new data and new challenges emerge. The ongoing efforts by Revidia Therapeutics will be crucial in determining whether Trodusquemine can finally translate its profound preclinical promise into a tangible clinical benefit for patients with DMD.

XI. Conclusion

Trodusquemine (MSI-1436) is a naturally derived aminosterol with a unique allosteric mechanism of Protein Tyrosine Phosphatase 1B (PTP1B) inhibition and an exceptionally broad range of compelling preclinical activities spanning metabolic, cardiovascular, neurodegenerative, oncologic, and regenerative medicine. Its ability to cross the blood-brain barrier and directly interact with cell membranes to displace toxic protein oligomers further adds to its multifaceted pharmacological profile.

Despite initial promise in early-phase clinical trials for obesity and type 2 diabetes, its development for these widespread indications was hampered by significant challenges, including poor oral bioavailability and the financial dissolution of its primary developer. Subsequent investigation in metastatic breast cancer also did not lead to advancement.

Currently, the most promising path forward for Trodusquemine lies in its development by Revidia Therapeutics for the treatment of Duchenne muscular dystrophy (DMD)-associated cardiomyopathy, for which it has received FDA Orphan Drug Designation. This strategic focus leverages its potent tissue regenerative capabilities, particularly in cardiac muscle, which are reportedly achieved at doses lower than those required for systemic metabolic effects, and utilizes a subcutaneous formulation to bypass oral absorption issues. The ongoing IND-enabling studies by Revidia are critical, with plans to initiate clinical trials in this patient population in 2025.

The development of analogs like DPM-1001, with improved oral bioavailability and its own orphan drug designation for Wilson Disease, indicates that the core therapeutic concept of modulating PTP1B with this class of aminosterols remains highly attractive and that the pharmaceutical limitations of Trodusquemine itself may be surmountable through further medicinal chemistry.

In conclusion, Trodusquemine stands as a molecule of significant scientific interest with a complex development history. While its journey has been marked by substantial obstacles, its profound and diverse biological activities, particularly its PTP1B inhibition and regenerative potential, continue to justify ongoing investigation. The success of current and future clinical trials, especially in the context of DMD, will be pivotal in determining whether Trodusquemine or its improved analogs can ultimately fulfill their considerable therapeutic promise.

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